1. Field of the Invention
The present invention relates to a foldable portable telephone set and, more particularly, to a foldable portable telephone set with an automatic off-hook function.
2. Description of the Prior Art
In a portable telephone set, upon reception of an incoming call, a ringing tone is generated and at the same time a termination light-emitting portion (e.g., an LED) is turned on, or flashes in order to inform the user of this. The user depresses a speech communication start key or a key having a similar function to go off hook, so that he or she can start a speech communication.
A foldable portable telephone set has two states, i.e., folded and open and calls may arrive in both states. Usually, the user carries the portable telephone folded, and accordingly calls are received in this state more often. When an incoming call is received as the telephone set is folded, the user must perform two operations, i.e., opening the portable telephone set to start a speech communication, and depressing the speech communication start key to go off hook.
In a prior art, a function similar to a speech communication stat key (off-hook key) is merely assigned to a specific key that can be depressed even as the telephone is folded. In this case as well, two operations are needed, i.e., opening the portable telephone set and depressing the speech communication start key.
In the foldable portable telephone set, various control operations may be performed after whether the portable telephone set itself is folded or open is confirmed. For example, Japanese Unexamined Patent Publication No. 7-74691 discloses a technique for monitoring whether the portable telephone set is folded or open, in order to control power consumption. According to this technique, whether the portable telephone set is folded or open is determined by using a photosensor and an LED which constantly flashes when the power supply is ON.
In the conventional foldable portable telephone set, when an incoming call is received as the telephone set is folded, two operations of opening the portable telephone set and depressing the speech communication start key are required. These series of operations are tedious for the user to perform.
If whether the portable telephone set is folded or open is to be monitored by using a photosensor and an LED which flashes constantly, the power consumption of the LED increases. This cuts the wait time and speech communication time of the portable telephone set short.